Project Summary Breast cancer is the most common type of cancer diagnosed and the second cause of cancer death in sub-Saharan African women. The few studies on breast cancer survival in this region reported low short-term survival rates, but none were able to comprehensively address reasons for low survival, how to improve survival, nor assess five-year and longer-term survival and survivorship. Further, the impact of more aggressive molecular subtypes, common in women of African-descent, on breast cancer survival in sub-Saharan Africa has not yet been investigated. The African Breast Cancer-Disparities in Outcomes (ABC-DO) study is a five-country sub-Saharan African breast cancer cohort initiated in 2014. During 3 years of recruitment, over 2100 women were recruited in Uganda, Nigeria, Zambia, Namibia, and South Africa. In the proposed project, ABC-DO-Plus, we will build on ABC-DO ? namely the established collaborations, research staff, tumor collections, ethical and legal permissions; and novel and successful mobile-Health (mHealth)-implemented follow-up ? to actively follow-up women for a further 2 years to 5 years post-diagnosis, examine for the first time 5-year survival overall and by key prognostic factors, molecular subtypes, treatment availability, affordability and compliance, socioeconomic determinants and comorbidities present in this setting, particularly high BMI and HIV. Breast cancer survivorship research, i.e. the health of women with breast cancer post- treatment, has largely been neglected in sub-Saharan Africa. ABC-DO-Plus will examine, for the first time, longitudinal changes in health-related quality of life up to 5 years after a woman?s breast cancer diagnosis. ABC-DO-Plus will inform interventions needed to mitigate the excessive number of deaths of women with the disease, and improve the quality-of-life of survivors. Utilizing a within-African framework of five countries with different cancer care politics, but also representing individual socioeconomic and cultural diversity, will enable comparisons across settings and hereby identification of modifiable factors influencing BC survival. Furthermore, its findings on the proportions of more aggressive tumor molecular subtypes, and how these may affect survival, as well as on the impact on survival of comorbidities such as HIV, will be of relevance to other black women in the US and elsewhere. The success of the proposed ABC-DO-Plus, and its manifold goals, will be ensured through continuity of the experience of the previous 4+ years? ABC-DO fieldwork, its established research infrastructure, and the efficient mHealth follow-up approach of this unique cohort.